(1) Field of the Invention
The present invention relates to a process cartridge and an electrophotographic image forming apparatus for forming an image using the process cartridge.
The process cartridge is a cartridge into which charging means and development means, or cleaning means and an electrophotographic photosensitive member are integrally accommodated, and this cartridge can be detachably attached to an image forming apparatus body.
Another example of the process cartridge is a cartridge into which an electrophotographic photosensitive member and at least one of the charging means, the development means and the cleaning means are integrally accommodated, and the cartridge can be detachably attached to the image forming apparatus body.
Another example of the process cartridge is a cartridge into which at least the development means and the electrophotographic photosensitive member are integrally accommodated, and the cartridge can be detachably attached to the image forming apparatus body.
The electrophotographic image forming apparatus (image forming apparatus, hereinafter) includes an electrophotographic copying machine, an electrophotographic printer (e.g., LED printer, laser beam printer and the like), an electrophotographic facsimile machine, and an electrophotographic word processor.
(2) Description of the Related Art
Conventionally, an image forming apparatus using electrophotographic image forming process employs such a process cartridge method that a photosensitive member and process means acting on the photosensitive member are integrally accommodated in a cartridge, and the cartridge is detachably attached to an image forming apparatus body. According to the process cartridge method, since an operator (user) can perform maintenance of the apparatus himself or herself without asking a service man, the operability can remarkably be enhanced. Therefore, the process cartridge method is widely used in image forming apparatuses. When the process cartridge is attached to the image forming apparatus body, it is necessary to precisely maintain the positional relation between the process cartridge and the image forming apparatus body when the attaching operation of the process cartridge is completed while maintaining an appropriate operating feeling.
As a method which is widely used for positioning the process cartridge with respect to the image forming apparatus and for maintaining the position, there is a method in which the process cartridge is provided with a projection, the apparatus body is provided with a positioning portion with which the projection is engaged, and when the projection is engaged with the positioning portion, a spring applies a force to the process cartridge to latch the process cartridge (see patent document 1, FIG. 6 for example).
A conventional positioning and holding structure of a process cartridge (cartridge 110, hereinafter) with respect to the apparatus body will be explained using FIG. 6.
The cartridge 110 is provided with circular projections 150 as positioning means. The projections 150 are disposed on side surfaces of opposite ends of the cartridge frame in the longitudinal direction. The projection 150 projects outward of the cartridge frame in parallel to an axis of the photosensitive member drum incorporated in the cartridge 110.
The cartridge holding position of the side plate 160 of the image forming apparatus is formed with U-shaped grooves 170 (170Y, 170M, 170C, 170K) as positioning portions. The U-shaped grooves are disposed such that the circular projections 150 are precisely received at predetermined positions. A cartridge attaching space sandwiched by the pair of left and right side plates 160 is provided in the apparatus body. Guide members 161 (161Y, 161M, 161C, 161K) as cartridge attaching auxiliary means as shown in FIG. 6 are mounted on left and right side surfaces of the space. Each of the guide members 161 is provided with an inclined surface 161a for guiding the process cartridge 110 of the guide member 161. The inclined surface 161a is inclined diagonally downward.
Linear springs 162 (162Y, 162M, 162C, 162K) as latches for holding the cartridge 110 are mounted on the apparatus body. A tip end of the linear spring 162 is formed with a sandwiching portion for sandwiching a bottom of the U-shaped grooves 170 from left and right sides. A distance between the narrowest portions of the sandwiching portion is smaller than a diameter of the circular projection 150 of the cartridge.
A procedure for attaching the cartridge 110 to the apparatus body will be explained. First, the opening and closing portion of an exterior (not shown) of the apparatus and the transfer belt unit are opened, and as shown in the cartridge 110K in FIG. 6, a bottom surface 110a of the cartridge 110 is inserted into the apparatus such that the bottom surface 110a is dropped thereinto along the inclined surface 161a of the guide member 161. Next, as shown in the cartridge 110M in FIG. 6, the projection 150 is dropped into the U-shaped grooves 170, the projection 150 rides over the tip end sandwiching portion of the linear spring 162 and is abutted against the bottom of the U-shaped grooves 170. At that time, the projection 150 is sandwiched by the sandwiching portion of the linear spring 162, and the cartridge 110 is secured to the side plate 160 of the apparatus body by the sandwiching force.
According to the image forming apparatus of the patent document 1, however, the sandwiching force of the linear spring 162 against the projection 150 of the cartridge 110 acts as a resistance when the cartridge is dropped. Since the projection 150 and the linear spring 162 always in contact until the projection 150 abuts against the bottom of the U-shaped grooves 170, this resistance acts until last when the cartridge 110 is positioned to the normal position. As a result, the insertion becomes insufficient, the cartridge floats or rides over, and the cartridge is not positioned to the normal position. With this behavior of the photosensitive member drum incorporated in the cartridge is also varied, and this affects an image formed by the photosensitive member drum in some cases. Further, excessive load is applied also to the transfer belt unit which is opposed to and abuts against the photosensitive member drum, the image forming region of the belt is damaged, this affects the image formation, the image quality is deteriorated, and the parts are damaged in some cases.
If the cartridge 110 is repeatedly detached and attached, the sandwiching portion of the linear spring 162 shaves the projection 150 of the cartridge and with this, the operating feeling when the cartridge is inserted becomes improper. The sandwiching force at the time of latch is reduced, reliable positioning and securing operation can not be carried out, and this affects the image formation in some cases.
As described in patent document 2 (Japanese Patent Application Laid-open No. 2000-181329), to enhance the attaching and detaching operation of the process cartridge, there is a conventionally proposed structure using a toggle latch. FIG. 7 is a diagram used for explaining an attaching and detaching structure of another conventional process cartridge.
In FIG. 7, a process cartridge 202 includes a projecting to-be-held portion 202a. An image forming apparatus body 214 includes a reference surface 291 for positioning the process cartridge 202 which is attached, a holding member 270 which is rotatably supported by the image forming apparatus body 214 and which has a first surface 271 and a second surface 272, and a force-applying member 280 for applying a force to the holding member 270. The holding member 270 can assume a first attitude in which the holding member 270 receives rotation moment from the force-applying member 280 and pushes and holds the to-be-held portion 202a of the process cartridge 202 in an attaching direction of the process cartridge 202 in the first surface 271, and a second attitude in which the holding member 270 receives rotation moment in a direction opposite from the first attitude of the holding member 270 from the force-applying member 280 and pushes the to-be-held portion 202a of the process cartridge 202 in the attaching and detaching direction of the process cartridge in the second surface 272.
With the above structure, when the process cartridge is attached to the image forming apparatus body, the process cartridge is pulled in, and when the process cartridge is attached to and detached from the image forming apparatus body, the process cartridge can be pushed out. Therefore, the attaching and detaching operability of the process cartridge is remarkably enhanced.
[Patent Document 1] Japanese Patent Application Laid-open No. H11-174940
[Patent Document 2] Japanese Patent Application Laid-open No. 2000-181329
According to the image forming apparatus of the patent document 2, however, although it is possible to prevent the operability from being deteriorated, since the insertion of the cartridge is insufficient, the cartridge is not positioned to the normal position in some cases. This affects an image to be formed, and the transfer belt is damaged in some cases.